1. The Field of the Invention
The present invention relates to apparatus and methods for light activation of hardening material. More particularly, the present invention is directed to apparatus and methods for activating dental compositions on a person's teeth. The apparatus and methods for activating dental compositions utilize a fiber optic funnel configured to focus radiant energy on a tooth of a person being treated.
2. Relevant Technology
Hardenable materials which are activated by radiant energy are commonly used in dentistry as sealants, adhesives and as filling material in dental preparations. Such hardenable materials are typically activated by exposure to radiant energy in a preselected spectral range, typically in either the long-wave ultraviolet light or blue visible spectrum. The light utilized to activate the hardenable material, or more specifically the photocurable material, is typically tailored specifically to the type of material.
A light curing unit containing a reflector lamp is used to irridate the photocurable material by directing light from the reflector lamp through a light guide positioned with its distal end adjacent to the photocurable material to be cured. The light guide functions to channel the light to the material located on a dental substrate during a dental procedure.
FIG. 1 schematically depicts a source of light 10 as utilized in a conventional light curing unit and light guide. FIG. 1 corresponds with FIG. 1 of U.S. Pat. No. 5,371,826, which is incorporated herein by reference. The source of light comprises a lamp filament 12 and a parabolic reflector 11; the light source is an example of means for generating light and then providing light to a light guide. The lamp filament 12 is disposed on the optic axis 13 within the light source 10 to reflect cones of light 17 off the reflector 11 toward a focal spot where light guide 15 is positioned. Light guide 15 has a light-receiving surface 14 oriented perpendicular to the optic axis 13 to receive the incident cones of light 17. The cones of light 17 are received at an acceptance angle which for maximum efficiency, should be as large as possible. The mathematical sine of the maximum acceptance angle, known as the numerical aperture, is determined by the optical properties of the fiber optic material and its shape The diameter of the light guide 15 at the light-receiving surface 14 is selected to maximize the efficient collection of light incident at the focal plane, coinciding with the light-receiving surface 14, and is generally in a range of between 8-13 mm. It is conventional for light guide 15 to have a curved end section 16 to satisfy the requirements of maneuverability and accessibility of the light guide 15 for placement in the oral cavity of a dental patient. The curved section 16 has a radius of curvature which is chosen in proportion to the diameter of the curved end of the light guide 15, with an angle of curvature of from, thirty degrees (30.degree.) to sixty degrees (60.degree.), for a diameter range of between about 8 mm to about 16 mm.
Conventional light guides are generally either fiber optic conductors or are solid conductors formed from glass or plastic. Light guides formed with fiber optics typically contain multiple strands of glass fiber held together as a flexible bundle or as a solid rod of fused individual fibers.
The use of such light guides with light curing units enables a dental practioner to rapidly harden compositions such that many dental procedures can be efficiently completed. It is often difficult, however, to direct sufficient light to only a small specific area without also directing light to areas which preferably do not receive any radiant energy. Many conventional light guides have diameters of about 11 mm or about 8 mm which is often larger than a typical dental preparation. Accordingly, smaller diameter light guides, such as those having diameters of about 2 mm, are also available. However, using light guides with smaller diameters also results in less light being delivered to the photocurable material. Additionally, the need for light guides with different diameters increases the costs of dental procedures.
An attempt to overcome the problems associated with delivering an optimal amount of light to relatively small areas is disclosed in U.S. Pat. No. 5,371,826. U.S. Pat. No. 5,371,826 discloses a fiber optic light guide which is tapered for concentrated delivery of light. More specifically, the fiber optic strands bundled together in the light guide each have a taper such that the diameter of the guide is less at the distal end than it is at the proximal end. To form such a tapered light guide, each fiber optic strand may be separately tapered, bundled and then fused together or a length of solid fiber optic may be stretched to form an elongated stretched section of conical geometry wherein each strand is uniformly tapered over the stretched section.
While the tapered light guide disclosed in U.S. Pat. No. 5,371,826 may be useful to deliver more light to a smaller area than is possible with conventional light guides, the tapered light guide only minimizes the problems associated with activating photocurable materials on dental substrates. Although the distal end has a diameter that enhances the ability of the light guide to be placed into smaller openings, it is still inadequate for some uses such as in a deep and narrow preparation. As indicated at column 3, line 64 to column 4, line 13, the taper angle is preferably relatively small to minimize the loss of light due to the angle of incidence becoming smaller than the critical angle. Claim 3 indicates that the taper angle for each fiber optic strand is preferably less than 0.1.degree. and that the taper angle of the light guide is less than 5.degree.. Accordingly, the diameter at the distal end of the light guide is not significantly less than the diameter at the proximal end of the light guide. Additionally, while the tapered light guide increases the concentration of the light delivered to a particular surface area as compared to conventional light guides, it is preferably to have even greater concentration in some circumstances than such slight tapers can deliver. Further, such tapered light guides fail to eliminate the need for multiple light guides having different diameters.
Such tapered light guides deliver large amounts of light compared to similarly sized light guides, however, such claims are primarily supported when the amount of light delivered is measured as the amount coming out of the distal end of the light guides. Even though a tapered light guide delivers more concentrated light, the light still tends to flare outward such that the diameter of the area that receives the light is much greater than the diameter of the distal end of the light guide. In clinical use, the distal end of the light guide is typically offset from the target photocurable material at a distance which produces flaring. Accordingly, the amount of light delivered to the target area is substantially less than amount of light exiting the distal end of the light guide. Comparative measurements taken to determine the amount of light delivered when the distal end of a light guide is offset from the target by about 1 cm indicate that the amount of light delivered by conventional light guides is not significantly different from supposedly more powerful light guides. Additionally, the flaring effect may also result in heat being potentially transferred to surfaces which are not intended to be targeted.
One method of reducing the offset distance between a distal end of a conventional light guide and the target photocurable material is the use of light tips attached to a light guide as disclosed in U.S. Pat. No. 4,666,405, which is incorporated herein by reference. The light tip has one end which is cone-shaped and the other end is configured for coupling with the distal end of a light guide. FIGS. 2-5 depict light tips as disclosed in U.S. Pat. No. 4,666,405.
FIG. 2 depicts a conventional light curing unit 30 connected to the proximal end or reception end 42 of a light guide 40. A light tip 50 as disclosed in U.S. Pat. No. 4,666,405 is coupled onto the distal end or transmission end 44 of light guide 50. FIG. 3 is an enlarged perspective view of light tip 50, which shows it in greater detail. Coupling portion 52 of light tip 50 is integral with cone portion 54. Cone portion 54 terminates at an apex 56. Conventional light curing units such as the unit shown at 10 typically house the elements set forth above as comprising source of light 10. Light curing unit 10 is another example of means for generating light and then providing light to a light guide.
FIG. 4 depicts cone portion 54 of light tip 50 pressed into photocurable material 60 which minimizes the offset distance between the distal end 44 of the light guide 40. Cone portion 54 is also shown being simultaneously pressed against a relatively resilient matrix band 62 which is being utilized to contain material 60. By pressing cone portion 54 of light tip 50 against matrix band 62 and into material 60 while triggering the light, the tendency of the matrix band to contract due to the shrinkage effect of the polymerized material is minimized. As a result, when matrix band 62 is pushed to the proximal surface of the adjacent tooth 66, the space between tooth 64 and 66 has the desired dimensions. The procedure is then repeated as needed for each incremental layer. FIG. 5 depicts a tip 70 which is similar to tip 50 shown in FIGS. 2-5 except apex 76 of cone portion 74 is flattened to enhance the ability to push against a matrix band.
The tips disclosed in U.S. Pat. No. 4,666,405 are adapted to being pushed into a filing material as the tips are plastic. The use of plastic enables the tips to be inserted into the photocurable material with minimal adhesion of the material to the tip. Accordingly, the plastic tips can be reused. Additionally, even if it is necessary to discard the tips, the plastic tips are relatively in expensive as indicated at column 1, lines 54-56.
Forming tips from plastic, however, inherently limits the number of times that the tips can be utilized. After the plastic tips are inserted into photocurable material, the tips are autoclaved. After being used and autoclaved several times, it is eventually necessary to discard the tips. It would be preferable to utilize a tip that is formed from more durable materials than plastic.
While the use of the plastic tips disclosed in U.S. Pat. No. 4,666,405 minimizes the offset distance between the targeted photocurable material by requiring that the tip be introduced into the photocurable material, it would be preferable to increase the concentration of light delivered without necessitating the introduction of the tip into the material. The cone shape of the tip does concentrates some light at the apex of the cone portion, however, it is not significantly more than would be concentrated at that point when a plastic tip is not used. Additionally, as light rays exit the cone portion a significant portion of the light rays are reflected by the sides of the cone portion laterally away from the tip.
In view of the foregoing, it will be appreciated that what is needed in the art are apparatus and methods for concentrating the amount of light transmitted from a light guide to activate hardenable materials.
Additionally, it would be a significant advancement in the art to provide methods for hardening material which do not necessitate the insertion of the instrument into hardenable material.
It would be a further advancement in the art to provide methods for safely hardening materials located in small, narrow openings in a tooth.
There is also a need in the art to provide apparatus and methods for activating hardenable materials with an instrument that activates hardenable material at least primarily or entirely in the direction in which the instrument is pointed.
It would be yet another advancement in the art to provide apparatus and methods for activating hardenable materials with instruments that can be repeatedly used and autoclaved with impacting the usefulness of the instruments.
Such apparatus and methods for treatment of tooth surfaces are disclosed and claimed herein.